Method for reducing acid in hydrocarbons

ABSTRACT

A method, and use of, a surfactant is provided for reducing the total acid number (TAN) of produced hydrocarbons. The method may include introducing a surfactant to produced hydrocarbons, separating the surfactant from the produced hydrocarbons, and removing the surfactant and associated acid from the hydrocarbons. The cloud point of the surfactant may be used in the separating step of the method, and removal of the precipitate from the hydrocarbons may reduce the TAN of the hydrocarbons. The separation step may include forming an aqueous or intermediate phase that comprises the surfactant and associated acid.

INCORPORATION BY REFERENCE OF PRIORITY APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalPatent Application No. 61/909,874 filed Nov. 27, 2013, which is herebyincorporated by reference in its entirety.

FIELD

The present disclosure relates generally to a method, and use of asurfactant, for reducing total acid number (TAN) in producedhydrocarbons. More specifically, the present disclosure relates to amethod and/or a use of a surfactant for reducing TAN by forming aprecipitate comprising at least some of the acid content from theproduced hydrocarbons.

BACKGROUND

For transportation and refining of produced hydrocarbons it is generallypreferable that the acid content in the produced hydrocarbons remainsbelow a particular threshold in order to avoid or reduce corrosion ofpipelines and refining facilities. Acids may include carboxylic acidssuch as naphthenic acids, and acids arising from H₂S content in producedhydrocarbons, which may give rise to naphthenic and sulfidic corrosion.One way to quantify the acid content of produced hydrocarbons is by anacidity measurement which yields a Total Acid Number (TAN) for theproduced hydrocarbon sample. Specifically, TAN is a measurement of thenumber of milligrams of potassium hydroxide required for neutralizationof acids in a single gram of oil. Produced hydrocarbons may have a TANnumber as high as 10-12 in some parts of the world. For transport andrefinement, it may be desirable to have a TAN less than 1. In NorthAmerica, TAN of 1.5-3 is common in produced hydrocarbons. A TAN greaterthan 1 can reduce the value of produced hydrocarbons.

Methods for reducing TAN may include, for example, caustic washing toremove naphthenic acids in gasoline and kerosene. However, this approachcan fail when applied to heavier feedstocks with high TAN due to theformation of very stable emulsions. An approach by refineries involvesreacting acid content with alcohols to reduce TAN, however, this processis reversible, which can diminish its effectiveness once the oil isfurther treated/refined. Acids can be destroyed by thermal treatment orcracking to generate carbon dioxide gas and low acid hydrocarboncontent, however, some undesirable side reactions can occur resulting inthe formation of sediments and gums that negatively impact the value ofthe crude. Adsorption on solid surfaces and the use of solventextraction can also be approaches to extracting naphthenic acids fromoil, however, losses in profits due to overall volume reduction can makesuch processes unattractive. Generally, treatments and processes forreducing high acid content in produced hydrocarbons add time and expenseto transportation and refining operations.

A need exists to reduce the TAN in produced hydrocarbons, for examplebitumen, to allow for transport and/or refining or processing of thebitumen with reduced or minimized corrosive effects on the associatedtransport, refining or processing equipment or components.

SUMMARY

In one embodiment, a method of for reducing a total acid number (TAN) inproduced hydrocarbons, is described, the method comprising: a)introducing a surfactant to the produced hydrocarbons to solubilize,associate, complex, or encapsulate acid in the produced hydrocarbons;separating the surfactant and solubilized, associated, complexed, orencapsulated acid from the produced hydrocarbons; and removing thesurfactant and solubilized, associated, complexed, or encapsulated acid.

In a further embodiment of the method or methods outlined above, thesurfactant solubilizes, associates, complexes, or encapsulates acid inthe produced hydrocarbons at temperatures below a cloud point of thesurfactant increasing the temperature above the cloud point to induceprecipitation.

In a further embodiment of the method or methods outlined above, theintroduced surfactant is soluble in the produced hydrocarbons attemperatures below a cloud point of the surfactant.

In a further embodiment of the method or methods outlined above, thesurfactant hydrophilic-lipophilic balance (HLB) is about 1 to 8.

In a further embodiment of the method or methods outlined above, thecloud point is manipulated by addition of salt.

In a further embodiment of the method or methods outlined above, thesalt is sodium chloride or ammonium sulfate.

In a further embodiment of the method or methods outlined above, thesodium chloride is added to or above a concentration of between about30,000 ppm or 80,000 ppm.

In a further embodiment of the method or methods outlined above, thesurfactant is precipitated by adjusting the temperature of the producedhydrocarbons to or above about 70° C.

In a further embodiment of the method or methods outlined above, in stepb) the surfactant and solubilized, associated, complexed, orencapsulated acid are formed in an aqueous phase or intermediate phasefor removal in step c).

In a further embodiment of the method or methods outlined above, in stepb) the surfactant and solubilized, associated, complexed, orencapsulated acid are formed in a microemulsion for removal in step c).

In a further embodiment of the method or methods outlined above, the HLDof the produced hydrocarbons following step a) is adjusted to about 0thereby forming the solubilized, associated, complexed, or encapsulatedacid substantially in the intermediate phase.

In a further embodiment of the method or methods outlined above, the HLDof the produced hydrocarbons following step a) is adjusted to benegative thereby forming the solubilized, associated, complexed, orencapsulated acid substantially in the aqueous phase.

In a further embodiment of the method or methods outlined above, theacid is a carboxylic acid.

In a further embodiment of the method or methods outlined above, theproduced hydrocarbons comprise oil, bitumen, diluted bitumen, crude,heavy oil or treated bitumen.

In a further embodiment of the method or methods outlined above, thesurfactant is non-ionic.

In a further embodiment of the method or methods outlined above, thesurfactant is an ethoxylated or propxylated alcohol, an alkylpolyglycoside, or a combination thereof.

In a further embodiment of the method or methods outlined above, thesurfactant is a combination of two or more surfactants.

In a further embodiment of the method or methods outlined above, theintroduced surfactant is mixed with the produced hydrocarbons prior tostep b).

In a further embodiment of the method or methods outlined above, mixingof the introduced surfactant and the produced hydrocarbons is performedduring step b).

In another embodiment, use of a surfactant for separating acid fromproduced hydrocarbon into an emulsion, microemulsion, intermediatephase, aqueous phase, or precipitate is described.

In a further embodiment of the use or uses outlined above, thesurfactant is non-ionic. In a further embodiment of the use or usesoutlined above, the acid is a carboxylic acid. In a further embodimentof the use or uses outlined above, the surfactant is an ethoxylated orpropoxylated alcohol, an alkyl polyglycoside, or a combination thereof.

In a further embodiment of the use or uses outlined above, thesurfactant is a combination of two or more surfactants.

In another embodiment, a method of separating acid from producedhydrocarbons, the method comprises a) introducing a surfactant to theproduced hydrocarbons to solubilize, associate, complex, or encapsulateacid in the produced hydrocarbons; and b) forming an intermediate oraqueous phase comprising the surfactant and solubilized, associated,complexed, or encapsulated acid.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described, by way ofexample only, with reference to the attached Figures. The patent orapplication file contains at least one drawing executed in color. Copiesof this patent or patent application publication with color drawing(s)will be provided by the Office upon request and payment of the necessaryfee.

FIG. 1 shows a flow chart illustrating steps of one example of a methodfor reducing the total acid number (TAN) of produced hydrocarbons. Theillustrative method comprises the steps of introducing a surfactant toproduced hydrocarbons, precipitating the surfactant from thehydrocarbon, and removing the precipitate from the hydrocarbon, therebyreducing the TAN of the hydrocarbon;

FIG. 2 shows a flow chart illustrating steps of one example of a methodfor reducing the total acid number of produced hydrocarbons. The methodcomprises the steps of introducing a surfactant to producedhydrocarbons, adjusting the temperature of the hydrocarbon containingthe surfactant to a temperature at or beyond the cloud point of thesurfactant thereby producing a precipitate, and removing the precipitatefrom the hydrocarbon, thereby reducing the TAN of the hydrocarbon;

FIG. 3A illustrates steps of one example of a method for reducing thetotal acid number of produced hydrocarbons. The illustrative methodcomprises the steps of introducing a surfactant to produced hydrocarbons[a] to produce hydrocarbon containing a surfactant [b]; precipitatingthe surfactant from the hydrocarbon to produce hydrocarbon containing aprecipitate [c]; and removing the precipitate from the hydrocarbon,thereby producing hydrocarbon with reduced TAN [d];

FIG. 3B illustrates two examples of a methods for reducing the totalacid number of produced hydrocarbons. The illustrative methods beginwith a produced hydrocarbon phase and an aqueous phase (the aqueousphase may be added to the produced hydrocarbons, or the producedhydrocarbons may already include an aqueous phase) to which is added asurfactant. Depending on the conditions of the system, for example theHLD, an emulsion or microemulsion of Type I (surfactant/acidsubstantially in the aqueous phase) or type III (surface/acidsubstantially in an intermediate phase) may be generated;

FIG. 4 illustrates one example of surface facilities for reducing thetotal acid number of produced hydrocarbons. As shown in the top sectionof FIG. 4, degassing (i.e. separating gas from oil, water, or anoil/water emulsion), free water knockout (i.e. water separation fromoil), and/or other treatment steps (i.e. further oil separation fromwater) may be performed on produced hydrocarbons (i.e. fluids producedfrom a hydrocarbon reservoir, optionally including oil/water emulsionsand gases) in suitable surface facilities. At various points duringprocessing (for example, those indicated by a “*” in the top section ofFIG. 4), surfactant may be added (optionally along with, for example,alcohol and/or salt) to, and mixed with, the produced hydrocarbons.Water, surfactant, and acid may then be removed from the producedhydrocarbons, reducing the TAN of the produced hydrocarbons as shown inthe bottom section of FIG. 4. This processing step may be repeated,optionally in series, in order to further reduce TAN. The processingstep shown in the bottom section of FIG. 4 may be performed once, oroptionally more than once as part of the process outlined in the topsection of FIG. 4;

FIG. 5 shows experimental vials and phase behaviour for data sets 1 (A),2 (B), 3 (C), 4 (D), and 5 (E) of Table 1;

FIG. 6 shows experimental vials and phase behaviour for data sets 6 (A),7 (B), and 8 (C) of Table 2;

FIG. 7 contains Table 1 which provides experimental data sets 1-5obtained from TAN reduction and phase behaviour experiments employingBASF DO5 surfactant; and

FIG. 8 contains Table 2 which provides experimental data sets 6-8obtained from TAN reduction and phase behaviour experiments employingSasol TDA-6 surfactant.

DETAILED DESCRIPTION

Described herein are methods, techniques, embodiments, systems andapparatuses for reducing total acid number (TAN) in producedhydrocarbons. It will be appreciated that the methods, uses andembodiments described herein are for illustrative purposes intended forthose skilled in the art and are not meant to be limiting in any way. Incertain non-limiting embodiments, the methods are capable of reducingthe TAN in produced hydrocarbons, such as bitumen, and involve the useof a surfactant and take advantage of the cloud point characteristic ofthe surfactant by precipitating at least some of the acid in theproduced hydrocarbons. Removal, or at least partial removal, of theprecipitate thereby at least partially reduces the TAN. It will beappreciated that the methods, systems, apparatuses, techniques andembodiments described herein are for illustrative purposes intended forthose skilled in the art and are not meant to be limiting in any way.All reference to dimensions, capacities, embodiments or examplesthroughout this disclosure, including the Figures, should be considereda reference to an illustrative and non-limiting embodiment or anillustrative and non-limiting example.

It will be appreciated that generally, surfactants are compounds thatlower the surface tension of a liquid, the interfacial tension betweentwo liquids, or the interfacial tension between a liquid and a solid. Asurfactant can be classified according to the composition of itsdifferent chemical functional groups. The hydrophilic part of asurfactant is referred to as the head of the surfactant, while thehydrophobic part of a surfactant is referred to as the tail. Surfactantsmay be ionic, zwitterionic, or non-ionic. An ionic surfactant carries anet positive (cationic) or negative (anionic) charge that is balanced bya counter-ion of the opposite charge, e.g., benzalkonium chloride iscationic with a chloride counter-ion and sodium lauryl sulphate isanionic with a sodium counter-ion. A zwitterionic surfactant possesses ahead with two oppositely charged groups, e.g., lecithin, making thesurfactant neutral overall.

Without wishing to be limiting in any way, it is envisioned that some orall of the following steps may be performed when carrying out anembodiment of a method as illustrated in FIG. 1:

-   -   Introducing a surfactant to produced hydrocarbons in step 10;    -   Adjusting the produced hydrocarbons to a cloud point of the        surfactant thereby precipitating the surfactant, acid captured        or bonded by the surfactant or micelle thereof, acid, or        combinations thereof, from the produced hydrocarbons in step 20;        and    -   Removing the precipitate from the hydrocarbon in step 30.

It will be appreciated that the cloud point may be manipulated usingknown methods including but not limited to the addition or removal ofsalt and/or alcohol, in the produced hydrocarbons, the composition ofthe hydrocarbons, pH, etc.

In a further embodiment, mixing of the introduced surfactant and theproduced hydrocarbons may be performed. In one embodiment, a mixing stepmay be performed during and/or after introduction of the surfactant tothe produced hydrocarbons. In another embodiment, a mixing step may beperformed during the step of precipitation. In yet another embodiment,mixing may be performed both during and/or after introduction of thesurfactant to the produced hydrocarbons, and during the step ofprecipitation.

The flow chart in FIG. 1 is illustrative of the above described method,which comprises the steps of introducing a surfactant to producedhydrocarbons to produce a hydrocarbon and surfactant mixture orsolution; precipitating the surfactant from the hydrocarbon andsurfactant mixture or solution to produce produced hydrocarbonscontaining a precipitate; and removing the precipitate to produce ahydrocarbon, such as bitumen or a produced bitumen, treated or dilutedbitumen, for example, with a reduced TAN.

A wide variety of surfactants are known in the art. Non-limitingexamples of known surfactants may be found in, for example, Surfactantsand Interfacial Phenomena, Rosen et al., 2012, John Wiley & Sons;Nonionic Surfactants: Alkyl Polyglucosides, Surfactant Science, DieterBalzer & Harald Luders, eds., 2000, Taylor & Francis, Vol. 91; andNon-Ionic Surfactants, Pierce L. Wendt & Demario S. Hoysted, eds., 2010,Nova Science Publishers; which are incorporated herein by reference. Theintroduced surfactant may comprise a non-ionic surfactant, which maycomprise a hydrophilic, uncharged head and a hydrophobic tail. In otherembodiments, more than one surfactant may be used to achieve a reductionin TAN. For example, the surfactant may be an ethoxylated orpropoxylated alcohol, such as Brij® 52 (polyethylene glycol hexadecylether) or Pluronic® L61 (a difunctional block copolymer surfactantterminating in primary hydroxyl groups), respectively. Additionally, thesurfactant may optionally be an alkyl polyglycoside. In anotherembodiment, the surfactant may be a combination of surfactants used as amixture or sequentially.

In a further embodiment, introduction of a surfactant to producedhydrocarbons may solubilize, complex, associate with, or encapsulateacid in the produced hydrocarbons in a temperature range that does notcross the cloud point of the surfactant. Typically, the acid in theproduced hydrocarbons, for example bitumen, produced bitumen, treated ordiluted bitumen, crude or heavy oil, includes a carboxylic acid, forexample, a naphthenic acid.

Without wishing to be bound by theory, it is postulated thatintroduction of a non-ionic surfactant to produced hydrocarbons maysolubilize, complex, associate with, or encapsulate acid in the producedhydrocarbons at temperatures below the cloud point of the surfactant.The non-ionic surfactant may comprise a polar moiety with an affinityfor acids, and may form micelles which incorporate acid molecules. Acidcontent may not necessarily be captured at the centre of the micelles.Rather, acid molecules may form part of the micelles, given that acidsare also polar species with some affinity for water and some affinityfor oil. Typically, the acid may be a carboxylic acid such as naphthenicacid.

Those skilled in the art will recognize that the cloud point is aphysical property of surfactants in a solution, and may be defined as aspecific temperature at which the surfactant precipitates, creating acloudy mixture. For non-ionic surfactants, reaching a cloud point of asolubilized surfactant may require heating. In other cases, or for othersurfactants, other physical or chemical property changes may be used toprecipitate the surfactant, for example, the introduction of one or moreadditional reagents and/or compounds, such as salts, may be used toprecipitate the surfactant. In another embodiment, cooling or a pHchange may be used to precipitate the surfactant.

The addition of salt may be used to precipitate the surfactant. Forexample, sodium chloride (NaCl) or ammonium sulfate ((NH₄)₂SO₄) may beused to increase the salt content of the produced hydrocarbons, causingprecipitation of the surfactant. In a further embodiment, increasingNaCl content in the produced hydrocarbons to more than about 30,000 ppmmay be used to precipitate the surfactant.

Those skilled in the art will recognize that the surfactant may have anassociated hydrophilic lipophilic balance (HLB) value. As will beappreciated to those skilled in the art, a lower HLB indicates a moreoil-soluble (rather than water soluble) compound. In one embodiment, thesurfactant may have an HLB value of between about 1 and about 8.However, some surfactants may have an HLB higher than 8, for example,Pluronic® 17R4.

As outlined herein, introduced surfactant may be precipitated from theproduced hydrocarbons. In some embodiments, adjustment of thetemperature of the surfactant/hydrocarbon mixture, for example byheating, to, or beyond, the cloud point of the surfactant mayprecipitate the introduced surfactant from the produced hydrocarbons.Alternatively, precipitation of the surfactant may be accomplished byany of a wide variety of known methods for precipitating a compound froma solution, some of which are described above. In some non-limitingembodiments, the surfactant may be precipitated through the addition ofan additional reagent such as salt, referred to as “salting out”.

The precipitated surfactant, including precipitated acid, may then beremoved from the produced hydrocarbons, wherein removal of theprecipitated surfactant and by extension the precipitated acid reducesthe TAN of the produced hydrocarbons. Precipitation of the surfactantmay also precipitate some of the acid solubilized by, complexed with,associated with, encapsulated by, or part of the surfactant micelles.

It will be appreciated that suitable methods for removing a precipitatefrom a fluid may be used to remove the precipitated surfactant and/oracid from the produced hydrocarbons. Some non-limiting examples includefiltration, gravity separation, distillation, centrifugation, decanting,electrostatic separation and related methods. In one embodiment, gravityseparation in a separation vessel may be used for precipitate removal.

In another embodiment, TAN of produced hydrocarbons may be reduced byperforming a method involving the following steps outlined in FIG. 2:

-   -   Introducing a surfactant to produced hydrocarbons shown in step        40;    -   Adjusting the temperature of the produced hydrocarbons to or        above a cloud point of the surfactant, thereby generating a        precipitate shown in step 50; and    -   Removing the precipitate from the hydrocarbon shown in step 60.

In addition, mixing of the introduced surfactant and the producedhydrocarbons may be performed to help increase or optimize the effect ofthe surfactant and, in turn, TAN reduction.

For example, a mixing step may be performed during and/or afterintroduction of the surfactant to the produced hydrocarbons.Alternatively, a mixing step may be performed during the step ofadjusting the temperature of the produced hydrocarbons to or above thecloud point of the surfactant. Further, mixing may be performed bothduring and/or after introduction of the surfactant to the producedhydrocarbons, and during the step of adjusting the temperature to orabove the cloud point of the surfactant.

The flow chart shown in FIG. 2 is illustrative of the above-describedmethod, which comprises the steps of introducing a surfactant toproduced hydrocarbons to produce a hydrocarbon and surfactant mixture orsolution; adjusting the temperature to or beyond the cloud point of thesurfactant, producing hydrocarbons containing a precipitate; andremoving the precipitate to produce a hydrocarbon with a reduced TAN.The adjustment of temperature may involve heating the hydrocarbon andsurfactant mixture or solution.

Without wishing to be limited by theory, it should be understood thatsome embodiments of the TAN reduction methods disclosed herein may beperformed having regard to hydrophilic-lipophilic deviation (HLD)considerations and may not be dependent on the cloud point but ratherseparation of the acid solubilized, associated, complexed, orencapsulated with the surfactant via the phase behaviour. This may beaccomplished by capturing the surfactant with the solubilized,associated, complexed, or encapsulated acid in a separated phase fromthe oil, such as an aqueous or intermediate phase or in a emulsion ormicro-emulsion.

The choice of surfactant, and the conditions used for TAN reduction(i.e. salt type and concentration in solution and/or added to thesolution, the type of oil being processed, the temperature, and the typeand concentration of alcohol(s) in and/or added to the solution) affectthe HLD of the system, and can be selected so as to achieve a desirableHLD. Contrary to HLB, which is based on the surfactant, the HLD takesinto account several different parameters of the system.

There are three phase behaviours common in oil, water and surfactantsystems when they form a microemulsion. Two of these phase behavioursare outlined in FIG. 3B. The salinity of the aqueous phase is aparameter influencing which type of behavior occurs. In a Winsor Type Isystem, the surfactant forms an oil-in-water microemulsion in theaqueous phase. In a Winsor Type II system, the surfactant forms awater-in-oil emulsion in the oil phase. This behavior leads tosurfactant retention in the oil phase. In a Winsor Type III system, thesurfactant forms a microemulsion in a separate intermediate phasebetween the oil and aqueous phases. This phase is a continuous layercontaining surfactant, water and dissolved hydrocarbons. Surfactant andsolubilized, associated, complexed, or encapsulated acid present in theaqueous or intermediate phases may be considered as separated from theoil or hydrocarbon phase and may be removed using any suitable method,such as decanting, etc., thereby lowering the Total Acid Number of theproduced hydrocarbons.

In some embodiments, it is desirable to achieve an HLD of, about, ornear 0 (Winsor Type III). At an HLD of 0, there is no difference betweenthe hydrophilic and lipophilic interaction energies (Quintero et al.(Optimization of Microemulsion Formulations with Linker Molecules, SPE165207, 2013)); the surfactant has equal affinity for both the water andoil phases, and oil and aqueous phases separate from one another morequickly under these conditions. An HLD at or near 0 may be beneficialbecause it allows for separation of surfactant and solubilized,associated, complexed, or encapsulated acid generally formed in theintermediate phase from oil/water mixtures.

In some embodiments, the HLD may be negative (Winsor Type I) whichgenerally results in the surfactant and solubilized, associated,complexed, or encapsulated acid microemulsions forming in the aqueousphase thereby reducing the TAN of the produced hydrocarbons.

A number of conditions can affect the HLD value of a system. The personof skill in the art will be familiar with HLD and how it is calculated(for example, see Salager et al. (Formulacion de microemulsiones por elMétodo del HLD, Techniques do I'Ingénieur, Vol. Génie des Procédés,articulo J2 157, 1-20 (2001)), Salager and Anton (Chapter 8: IonicMicroemulsions, Handbook of Microemulsion Science and Technology, P.Kumar and K. L. Mittal, eds., Marcel Dekker, New York (1999)), andQuintero et al. (Optimization of Microemulsion Formulations with LinkerMolecules, SPE 165207, 2013), each of which is herein incorporated byreference).

For illustrative purposes, HLD may be determined in an oil/aqueoussystem having a surfactant comprising ethylene oxide unit(s) as follows:

HLD=α−EON+b(sal)−k(ACN)+t(ΔT)+a(A)   (1)

where α, k, and t (ct in Tables 1 and 2) are constants related to thesurfactant used;

EON refers to the number of ethylene oxide units per molecule ofsurfactant;

b is a constant of the salt in/added to the system;

sal is the salinity in mass percent in the aqueous phase of the system;

ACN is related to the type of oil/hydrocarbon and the number of carbonatoms in the oil/hydrocarbon, [Quintero et al. (Optimization ofMicroemulsion Formulations with Linker Molecules, SPE 165207, 2013)];

ΔT is the temperature difference relative to a reference temperature(25° C.);

A represents the weighted percentage of alcohol in/added to the system;and

a is a constant characteristic of the alcohol in/added to the system andthe surfactant in/added to the system.

Values for the constants in equation (1) are known in the art, and maybe found, for example, in Salager et al. (Formulacion de microemulsionespor el Método del HLD, Techniques do I'Ingénieur, Vol. Génie desProcédés, articulo J2 157, 1-20 (2001)), herein incorporated byreference.

A non-limiting illustrative embodiment may refer to a produced oilcontaining acid and some water, where the acid resides in the oil phaseof the oil/water mixture. A non-ionic surfactant may be added to theoil/water mixture, the surfactant being water soluble. In onepossibility, the temperature of the mixture may be increased, which maydrive the surfactant into the oil phase where it can solubilize/interactwith/capture the acid. When the cloud point of the surfactant isreached, the surfactant and associated acid may then precipitate out ofsolution in the aqueous phase, at which point the surfactant/acidcomponent can be separated from the produced oil, resulting in a TANreduction of the produced oil.

In a second possibility, the mixing of the surfactant with the oil/watermixture may produce an oil-in-water emulsion within which the surfactantmay solubilize the acid content. When heating is used to reach thesurfactant cloud point, the oil-in-water emulsion may destabilize,allowing the surfactant/acid component to precipitate out of solution inthe aqueous phase, which can then be separated from the produced oil,resulting in TAN reduction of the produced oil.

It will be appreciated that water may be added to the methods describedherein in order to provide for an aqueous phase if necessary or desired.

EXAMPLE 1 Reducing Tan Using a Surfactant

An example of a method for reducing TAN in bitumen is described infurther detail below with reference to FIG. 3A.

As illustrated, in step 200 a surfactant, for example a non-ionicsurfactant, such as an ethoxylated alcohol or propoxylated alcohol, isintroduced to produced hydrocarbons [a], having a TAN higher thandesired, to produce [b] a hydrocarbon and surfactant mixture. Productionof [b] may optionally be assisted by a mixing step. The surfactant inthe produced hydrocarbons may form micelles, containing, incorporated orassociated to acid, for example a carboxylic acid. In step 210, aprecipitation is performed to produce produced hydrocarbons containing aprecipitate [c]. A mixing step may optionally be performed during step210. This precipitation may be triggered by heating the solution to atemperature at or above the cloud point of the introduced non-ionicsurfactant, producing a precipitate comprising the surfactant and atleast some acid. In step 220, the precipitate is removed from thehydrocarbon and precipitate mixture [c], for example by way ofcentrifugation or gravity separation in a separation vessel, followedby, for example, skimming, decanting or filtration to produce [d] ahydrocarbon with a reduced TAN.

The method illustrated in the example described herein may be carriedout for reducing the TAN of produced hydrocarbons using a surfactant.The produced hydrocarbons may be oil, bitumen, diluted bitumen, ortreated bitumen, including bitumen which has been produced from adeposit, such as an oil sands reservoir, and treated or diluted asnecessary or desired as would be appreciated by those in the art.

It will be appreciated that the produced hydrocarbons referred to hereinmay include any produced hydrocarbons including, but not limited to,heavy oil, bitumen, diluted bitumen, or treated bitumen that comprisesan acid or acidic component.

It will be appreciated that reference to a surfactant herein encompassesembodiments wherein a single surfactant is intended or a combination ofmultiple surfactants used in combination or delivered, added, orsolubilized sequentially. A combination of surfactants comprisingnon-ionic, cationic, anionic, or zwitterionic surfactants, orcombinations thereof, may be used.

It will be appreciated that reference to precipitation hereinencompasses embodiments wherein a precipitation encompasses aco-precipitation including a co-precipitation of surfactant and acid.

EXAMPLE 2 Tan Reduction Surface Facilities

An example of surface facilities and processes for reducing TAN inbitumen/produced hydrocarbons is described in further detail below withreference to FIG. 4.

As illustrated in the top section of the figure, degassing (i.e.separating gas from oil, water, or an oil/water emulsion), free waterknockout (i.e. water separation from oil), and/or other treatment steps(i.e. further oil separation from water) may be performed on producedhydrocarbons (i.e. fluids produced from a hydrocarbon reservoir,optionally including oil/water emulsions and gases) in suitable surfacefacilities. At various points during hydrocarbon processing (forexample, those denoted by a “*” in the top section of FIG. 4),surfactant may be added (optionally along with, for example, alcoholand/or salt) to, and mixed with, the produced hydrocarbons. Water,surfactant, and acid may then be removed from the produced hydrocarbons,reducing the TAN of the produced hydrocarbons as shown in the bottomsection of FIG. 4. In this non-limiting example, oil TAN was reducedfrom 1.4 to <1.4 using one iteration of the processing step shown at thebottom of FIG. 4. This processing step may be repeated, optionally inseries, in order to further reduce TAN. The processing step may beperformed once, or optionally more than once as part of the processoutlined in the top section of FIG. 4, and may optionally be performedat multiple points along the process outlined in the top section of FIG.4.

EXAMPLE 3 HLD AND TAN Reduction

Examples of TAN reduction using a surfactant (i.e. colloidal extraction)technique as described herein is described in further detail below andwith reference to FIG. 3B. HLD considerations are provided. Variables inthese experiments included the type of surfactant used (BASF D05surfactant and Sasol TDA-6 surfactant were tested), salinity of thesystem (ammonium sulfate at different concentrations was used),surfactant concentration (1 g and 5 g of surfactant per 100 mL waterconcentrations were tested), temperature (room temperature and 70° C.were tested), and alkalinity of the system (very little (˜0.0001M) NaOHwas used, ensuring that acid was being captured and removed rather thanneutralized).

Methods

EACN (Equivalent Alkane Carbon Number) Measurement Procedure:

Microemulsions were prepared by mixing 2 ml of aqueous phase and 2 ml ofoil phase in 2 dram flat bottom vials. The aqueous phase was prepared byadding the ionic reference surfactant, 30% w/v NaCl solution, anddeionized water. In the aqueous phase, the surfactant concentration wasmaintained at 10% w/v, whereas the amount of NaCl was varied from 0 to25 g/100 ml. The oil phase consisted of mixtures of diluted bitumen oil(80% bitumen, 20% hexane), and toluene in 1:3, 1:1, 3:1, and 1:0 dilutedbitumen oil to toluene mass ratios. All formulations in one data setwere mixed and left to equilibrate at room temperature (24° C.) on aflat surface. The phase behavior was recorded after 2 weeks.

Phase Behavior Studies Procedure:

Microemulsions were prepared by mixing 2 ml of a sample of dilutedbitumen oil and 2 ml of aqueous phase. The aqueous phase was prepared byadding a non-ionic surfactant, 40% w/v (NH₄)₂SO₄ solution, deionizedwater, and NaOH solution (in some cases) to 2 dram flat bottom vials. Inthe aqueous phase, the surfactant concentration was maintained at 1 or 5g/100 ml, whereas the amount of (NH₄)₂SO₄ was varied from 0 to 21 g/100ml. Subsequently, 2 ml of oil were added to each aqueous phase. Allformulations in one data set were gently mixed 20 times and left toequilibrate at room temperature (24° C.) on a flat surface. Optimumsalinities (S*) were identified as the middle phase bicontinuous μEwhere the excess phases separated in the shortest time. Optimumsalinities were observed within the first 15-30 min after preparation.The overall separation time was about 6 hrs, but the phase behavior wasrecorded after 24 hr.

Results:

Results of TAN reduction and phase behaviour studies are outlined inFIGS. 7 and 8 containing Tables 1 and 2, respectively. Tables 1 and 2provide parameters and results of systems using BASF DO5 surfactant andSasol TDA-6 surfactant, respectively, and ammonium sulfate salt. In allcases, the starting diluted bitumen oil had a TAN value of 1.4. Thephase behaviour values in Tables 1 and 2 indicate a general preferenceof the surfactant for the aqueous phase (denoted by a phase behaviour of1), the oil phase (denoted by a phase behaviour of 2), or the separationof the mixture into 3 phases (oil, an intermediate phase, and aqueous)(denoted by a phase behaviour of 3).

Table 1 contains data sets (scans) 1-5. In data set 1, BASF DOSsurfactant was used at a concentration of 5 g surfactant/100 mL water,the temperature was 25° C., and no NaOH was used. Salt concentration(ammonium sulfate) was increased moving from vial 1-12. HLD values foreach vial are provided. As shown in vial 1-8, TAN was reduced to 1.32following treatment. Experimental vials are shown in FIG. 5A.

In data set 2, BASF DO5 surfactant was used at a concentration of 1 gsurfactant/100 mL water, the temperature was 25° C., and no NaOH wasused. Salt concentration (ammonium sulfate) was increased moving fromvial 1-12. HLD values for each vial are provided. As shown in vials 2-7and 2-8, TAN was reduced to 1.23 and 1.09, respectively. Experimentalvials are shown in FIG. 5B.

In data set 3, BASF DO5 surfactant was used at a concentration of 5 gsurfactant/100 mL water, the temperature was 25° C., and 0.0001M NaOHwas used. Salt concentration (ammonium sulfate) was increased movingfrom vial 1-12. HLD values for each vial are provided. As shown in vials3-7 and 3-9, TAN was reduced to 1.1-1.2 and 1.05-1.15, respectively.Experimental vials are shown in FIG. 5C.

In data set 4, BASF DO5 surfactant was used at a concentration of 5 gsurfactant/100 mL water, the temperature was 70° C., and no NaOH wasused. Salt concentration (ammonium sulfate) was increased moving fromvial 1-12. HLD values for each vial are provided. As shown in vial 4-2,TAN was reduced to 0.95-1.05. Experimental vials are shown in FIG. 5D.In data set 5, BASF DO5 surfactant was used at a concentration of 5 gsurfactant/100 mL water, the temperature was 70° C., and 0.0001M NaOHwas used. Salt concentration (ammonium sulfate) was increased movingfrom vial 1-12. HLD values for each vial are provided. As shown in vial5-1, TAN was reduced to 1.25. Experimental vials are shown in FIG. 5E.

Table 2 contains data sets (scans) 6-8. In data set 6, Sasol TDA-6surfactant was used at a concentration of 1 g surfactant/100 mL water,the temperature was 25° C., and no NaOH was used. Salt concentration(ammonium sulfate) was increased moving from vial 1-12. HLD values foreach vial are provided. As shown in vials 6-5 and 6-7, TAN was reducedto 0.77 and 1.22, respectively. Experimental vials are shown in FIG. 6A.

In data set 7, Sasol TDA-6 surfactant was used at a concentration of 1 gsurfactant/100 mL water, the temperature was 25° C., and 0.0001M NaOHwas used. Salt concentration (ammonium sulfate) was increased movingfrom vial 1-12. HLD values for each vial are provided. As shown in vial7-7, TAN was reduced to 1.2-1.3. Experimental vials are shown in FIG.6B.

In data set 8, Sasol TDA-6 surfactant was used at a concentration of 1 gsurfactant/100 mL water, the temperature was 70° C., and 0.0001M NaOHwas used. Salt concentration (ammonium sulfate) was increased movingfrom vial 1-12. HLD values for each vial are provided. As shown in vials8-1 and 8-2, TAN was reduced to 1.32 and 1.35, respectively.Experimental vials are shown in FIG. 6C.

As will be clear from the data and trends described above and in FIGS.5-8, TAN of bitumen can be reduced using surfactant, as disclosedherein. The HLD value has an effect on the phase behaviour of thesystem, and on the amount by which TAN is reduced following a round ofprocessing. In some cases, it may be desirable to optimize or improveTAN reduction, or phase separation behavior, or both. In someembodiments, it may be desirable to achieve a balance between TANreduction and phase separation, such that TAN is reduced in a mannerthat allows for easy surfactant/acid separation during processing.

Although not shown in the Tables, it should be noted that in certainembodiments, an alcohol may be added to the system. In these cases, thealcohol addition may allow desirable TAN reduction and/or phasebehaviour properties to be achieved with the use of less surfactant.

One or more illustrative embodiments have been described by way ofexample. It will be apparent to persons skilled in the art that a numberof variations and modifications can be made without departing from thescope of the invention as defined in the claims.

What is claimed is:
 1. A method of reducing a total acid number (TAN) inproduced hydrocarbons, the method comprising: introducing a surfactantto the produced hydrocarbons to solubilize, associate, complex, orencapsulate acid in the produced hydrocarbons; separating the surfactantand solubilized, associated, complexed, or encapsulated acid from theproduced hydrocarbons; and removing the surfactant and solubilized,associated, complexed, or encapsulated acid.
 2. The method according toclaim 1, wherein the surfactant solubilizes, associates, complexes, orencapsulates acid in the produced hydrocarbons at temperatures below acloud point of the surfactant and while separating the surfactant andsolubilized, associated, complexed, or encapsulated acid from theproduced hydrocarbons, the temperature is increased above the cloudpoint to induce precipitation.
 3. The method according to claim 1,wherein the introduced surfactant is soluble in the producedhydrocarbons at temperatures below a cloud point of the surfactant. 4.The method according to claim 1, wherein the surfactanthydrophilic-lipophilic balance (HLB) is about 1 to
 8. 5. The methodaccording to claim 2, wherein the cloud point is manipulated by additionof salt.
 6. The method according to claim 5, wherein the salt is sodiumchloride or ammonium sulfate.
 7. The method according to claim 6,wherein the sodium chloride is added to or above a concentration ofbetween about 30,000 ppm and 80,000 ppm.
 8. The method according toclaim 1, wherein the surfactant is precipitated by adjusting thetemperature of the produced hydrocarbons to or above about 70° C.
 9. Themethod according to claim 1, wherein the surfactant and solubilized,associated, complexed, or encapsulated acid are formed in an aqueousphase or intermediate phase for subsequent removal.
 10. The methodaccording to claim 1, wherein the surfactant and solubilized,associated, complexed, or encapsulated acid are formed in amicroemulsion for subsequent removal.
 11. The method according to claim9, wherein the HLD of the produced hydrocarbons following introducingthe surfactant is adjusted to about 0 thereby forming the solubilized,associated, complexed, or encapsulated acid substantially in theintermediate phase.
 12. The method according to claim 9, wherein the HLDof the produced hydrocarbons following introducing a surfactant isadjusted to be negative thereby forming the solubilized, associated,complexed, or encapsulated acid substantially in the aqueous phase. 13.The method according to claim 1, wherein the acid is a carboxylic acid.14. The method according to claim 1, wherein the surfactant isnon-ionic.
 15. The method according to claim 1, wherein the surfactantis an ethoxylated or propxylated alcohol, an alkyl polyglycoside, or acombination thereof.
 16. The method according to claims 1, wherein thesurfactant is a combination of two or more surfactants.
 17. The methodaccording to claim 1, wherein the introduced surfactant is mixed withthe produced hydrocarbons prior separating the surfactant andsolubilized, associated, complexed, or encapsulated acid from theproduced hydrocarbons.
 18. The method according to any one of claims 1,wherein mixing of the introduced surfactant and the producedhydrocarbons is performed during separation of the surfactant andsolubilized, associated, complexed, or encapsulated acid from theproduced hydrocarbons.
 19. A method of separating acid from producedhydrocarbons, the method comprising introducing a surfactant to theproduced hydrocarbons to form an emulsion, microemulsion, intermediatephase, aqueous phase, or precipitate.
 20. A method of separating acidfrom produced hydrocarbons, the method comprising: introducing asurfactant to the produced hydrocarbons to solubilize, associate,complex, or encapsulate acid in the produced hydrocarbons; and formingan intermediate or aqueous phase comprising the surfactant andsolubilized, associated, complexed, or encapsulated acid.